[CustomNPCs mod] External folder for models?

Is there a way to load custom models into Minecraft to use with the Custom NPC's mod?

Here's the breakdown of why I'm asking: I added Digimobs to my mods folder, but when I loaded my game it gave me the error "Duplicate ID of 27." I cannot use it, but I still want to use the models with the current mod lineup I have.

Can the class files be put in some sort of external folder to be used with Custom NPCs?